In view of the dispersion phenomenon in the measurement of liquid refractive index by prism total reflection method，the original light source of sodium or mercury lamp was replaced by a laser，and the extinction phenomenon is observed by a camera，thus eliminating the influence of the complex spectral line on the measurement． Several liquids’refractive indexes under different wavelengths were measured with the improved device．The results show that the measured values are in accordance with the references with the relative uncertainty less than 0． 1%． The improved experimental method is easy to operate and has high accuracy，which has further application value．